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52" brushless yacht. Water jet powered

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52" brushless yacht. Water jet powered

Old 06-30-2020, 08:51 AM
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Over_torqued
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Default 52" brushless yacht. Water jet powered

Im looking to build my first larger boat. Ive done smaller ones 36" and less.
i just bought a 52" fiberglass yacht it comes with the top and bridge. Will post pics or a link as soon as it will let me.

I want to make a propulsion system similar to the yacht Azzam it has 4 water jets. 2 large water jets are centered and two smaller ones on the outside. Only the outside ones turn or reverse.
I have a few questions. Im going with two 50 or 55mm fixed position jets for the center and two 40mm turnable and reversible for the outside. What brushless motors would you recommend for each? The 40mm and 50mm

Its a large boat so i plan to have plenty of battery i realize i may be running four separate esc's to do this.
Also tbe two center jets will be controlled separately and used for boost in a straight line.

I am trying to research and not finding much on water jets this size.

Thanks. For any help and any suggestions are welcome.
Old 06-30-2020, 11:14 AM
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You’ll have to give us the specs of the jet units. What power level does the jet maker recommend? Motor size and KV are essential to know. That should be your first point of reference. Few here have much scratch built jet experience, you might try posting in the scale group too.

You will need four ESCs, the battery voltage and capacity will depend on the motors used and the run time desired. Your transmitter will also need some channel mixing or a separate mixer to control essentially three different motors independently. This will not be a simple build, perhaps you might consider a less complex jet drive system - although I understand the desire for something different.


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Old 07-01-2020, 07:56 AM
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You simply said most of what i said. I know the radio part and i figured the 4 esc's as i said in OP due to the size of motors needed. I did post specs or all the specs any jets that size say is the mm of the impeller. I just wanted to know how to size the motor to the jet.

Never found a direct answer but looking at smaller ones that come with a motor I have found its similar to a regular prop in that you want the motor diameter equal to or larger than the prop. I may be wrong this is just what i have found so far. Also most of the jet pumps seem to want 20,000rpm. This being known i think i know what motors to use now. The larger ones will have to run 6s while the smaller ones will be 3s. Due to the kv ratings. Not a problem as i planned to power them separately anyways. This will keep them within a reasonable rpm of each other and around 20,800rpm unloaded.

Still waiting on the yacht to come so i wont order until i can measure and make sure my planned jet sizes are appropriate. I will post results as they come.


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